DUAL POLARIZATION PLANAR ARRAY ANTENNA AND RADIATING ELEMENT THEREFOR

Description

1. Technical Field

[0001] The present invention relates to antennas and particularly to cavity backed antennas.

2. Related Art

[0002] One type of antenna suitable, for example, for satellite communication is planar array antennas. Planar array antennas are generally formed of an array of many (e.g., hundreds) cells, defined at least in part on printed circuit boards.

[0003] In a simple antenna, each cell includes a single electric probe, which either receives electromagnetic signals from a remote antenna (e.g., a satellite carried antenna) or transmits electromagnetic signals toward a remote antenna. A bottom reflective layer of the planar antenna reflects electromagnetic signals propagating downward, such that they reflect upwards toward the remote antenna.

[0004] It has been suggested to use a dual beam and dual polarization antenna, in which each cell includes two orthogonal electric probes, in separate layers, such that the probes share a common cell aperture. In order to prevent interference between the probes in a single cell, intra-cell isolation is required.

[0005] U.S. patent 5,872,545 to Rammos, the disclosure of which is incorporated herein by reference, describes such a dual beam and dual polarization antenna. Intra-cell isolation between the beams, however, is limited in the Rammos antenna and therefore the antenna can not be used in applications which are sensitive to signal polarization.

[0006] The problem of isolation between the beams of a single cell is compounded in relatively large planar arrays, which are used for transmissions over a relatively large bandwidth (e.g., for communications). In such arrays, also inter-cell isolation is required between the cells. In order to prevent interference between the cells, for example, each cell may be surrounded by a metallic frame. While such metallic frames improve the radiation efficiency of each cell, they interfere with the intra-cell isolation and make it even harder to use dual-polarization cells.

[0007] U.S. patent publication 2003/0122724 to Shelley et al., the disclosure of which is incorporated herein by reference, describes a planar array antenna with elements having two orthogonal probes. Features are described to increase isolation between the signals associated with each of the probes.

[0008] EP-A- 0 089 084 by de Ronde teaches an antenna for circularly polarized highfrequency signals comprising a succession of layers. A first insulating layer includes openings defined by metal plated walls forming miniature horns, each having a square cross-section. A dielectric layer adjacent the first insulating layer supports a first supply network for signals whose direction of polarization is of a first type of linear polarization. A second insulating layer includes openings defined by metal plated walls forming miniature waveguides each having the same square cross-section as a respective horn, at the side facing the first network, and having a rectangular cross-section at the other side. Another dielectric layer supports a second supply network for signals whose direction of polarization is perpendicular to the polarization of the signals of the first network. A third insulating layer includes openings defined by metal plated walls forming miniature waveguides each having the same rectangular cross-section as a respective waveguide in the second insulating layer, at the side facing the second network, and which has a depth smaller than the thickness of the third insulating layer. This document discloses the preamble of claim 1.

[0009] EP-A 0 481 417 by Raguenet teaches a feed device for a radiating element operating with dual polarisation, comprising a first feed line penetrating into a first cavity situated beneath the said radiating element, and a second feed line arranged according to a geometry orthogonal to the first line and penetrating into a second cavity situated In the continuation of the first, a conductive part forming a coupling slot between these two cavities.

[0010] WO-A-89109501 by Collins teaches a flat plate array antenna is formed of two or more plates (4, 5, 6) with a thin conductive sheet (45, 56) interposed between each pair of plates. The plates are configured to define horns and at least one open-sided channel which is closed by the conductive sheet to form a waveguide for supplying signals to or from the antenna. The plates may each be formed of moulded plastics material having a conductive layer over at least part of the surface and formed by metallisation of the plastics moulding.

[0011] The invention is defined by the features of independent claim 1.

[0012] The antenna may optionally include at least 10, 20, 50 or even 100 cells in a single antenna panel. In an exemplary embodiment, a single antenna panel may include over 200, 500 or even over a thousand cells. In some embodiments, the orthogonal electric probes may be capable of supporting two polarizations simultaneously.

[0013] Optionally, continuous electrical conductance is maintained along the entire height/depth of the cell enclosures, in order to improve the isolation between neighboring cells.

[0014] In some embodiments, the metallic enclosures of the cells are at least partially filled by dielectric fillers in order to lower the cutoff frequency of the cell and increase the cell's frequency response.

[0015] Optionally, several (e.g., 2-4) dielectric overlays may cover the tops of the cells in the transmission direction, to better match the cell's impedance with the open space impedance (377 ohms). This arrangement improves the radiation efficiency of the radiators and the array as a whole.

[0016] An aspect of some embodiments relates to a microwave planar antenna including a plurality of waveguide radiating cells having one or more layers (e.g., one or more cover layers) with different dielectric properties in different cells.

[0017] In some embodiments, the covers of different cells may have different dielectric properties according to average dielectric properties of a radome above each cell. Alternatively or additionally, different cells may have different dielectric properties in order to add a tilt angle to the view direction of the antenna.

[0018] In some embodiments, the covering dielectric layers may be parallel to the probes of the cells and differ in their dielectric value. Alternatively, some or all of the dielectric covers, of some or all of the cells, may be tilted at an angle relative to the probes of their respective cells. In some embodiments, at least some of the dielectric covers of at least some of the cells may have a non-uniform thickness and/or covers of different cells may have different thicknesses.

[0019] There is therefore provided in accordance with an embodiment of the invention, an RF antenna structure according to claim 1.

[0020] Optionally, the at least one radiation cell is adapted for transmission of waves of a predetermined frequency band and wherein the upper portion allows propagation of waves generated by the upper probe in the predetermined frequency band while the lower portion does not substantially allow propagation of waves generated by the upper probe, in the predetermined frequency band.

[0021] The lower portion of the enclosure is above the lower probe or below the lower probe. Optionally, the height of the upper portion of the enclosure is substantially equal to a quarter wavelength of a frequency that can pass through the upper portion but is blocked from passing below the upper portion. Optionally, the cross sectional area of the cell between the upper and lower probes is smaller than 100 square millimeters. Optionally, the cross-sectional area of the cell within the enclosure has a capital "T" shape over at least part of its height. Optionally, the antenna structure includes at least one dielectric cover above the cell conductive enclosure. Optionally, the at least one dielectric cover above the cell effectively isolates the cell from dirt and humidity in the environment. Optionally, the at least one dielectric cover is not perpendicular to a beam direction of the cell. Optionally, the at least one dielectric cover has a non-uniform thickness. Optionally, the enclosure comprises a metal ridge, smaller than the upper probe, serving as a single ridge waveguide structure.

[0022] There is further provided in accordance with an embodiment of the invention, a planar antenna array having a transmitting face and comprising a plurality of arrayed cells each cell comprising a first antenna probe, a second antenna probe spaced away from the first antenna and a reflector structure situated between the first and second antenna probes that is configured to pass RF waves transmitted/received by the second antenna probe and to reflect RF waves transmitted/received by the first antenna probe.

[0023] Optionally, the first antenna probe has a first RF polarization and the second antenna probe has a different RF polarization. Optionally, the reflector structure includes a waveguide section that passes RF waves with the polarization of the second antenna probe but is cut-off for RF waves with the polarization of the first antenna probe. Optionally, the reflector structure is spaced at a distance from the first antenna probe such that RF waves reflected from the reflector structure reinforce RF waves generated or received at the first antenna probe. The first and second antenna probes are oriented perpendicular to each other.

BRIEF DESCRIPTION OF FIGURES

[0024] Particular non-limiting exemplary embodiments will be described with reference to the following description in conjunction with the figures. Identical structures, elements or parts which appear in more than one figure are preferably labeled with a same or similar number in all the figures in which they appear, in which:

Fig. 1 is a schematic layout of a corporate feed conductor array for an antenna panel, in accordance with an exemplary embodiment;

Fig. 2 is an exploded view of a radiation cell, in accordance with an exemplary embodiment;

Fig. 3 is a schematic top view of an excitation probe of an antenna, within its respective frame, in accordance with an exemplary embodiment;

Fig. 4 is a cross-sectional view, taken parallel to the front of the exemplary antenna along dashed line A-A' in Fig. 2, of a lower enclosure and its respective dielectric filler, in accordance with an exemplary embodiment;

Fig. 5 is a cross-sectional view of the exemplary radiation cell of Fig. 2 beneath its upper probe, along dashed line B-B' in Fig. 2, in accordance with an exemplary embodiment; and

Fig. 6 is a schematic sectional view of an antenna panel beneath a radome, in accordance with an exemplary embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

General Structure

[0025] Fig. 1 is a schematic top view layout of a corporate conductive feed array for an exemplary antenna panel 100, in accordance with an exemplary embodiment. Antenna panel 100 includes a plurality of cells 102 at the distal end of each feed point which are connected in a corporate array of feed lines to a central single main feed line 104, in what is commonly referred to as a corporate feed network (CFN). Although only one CFN is shown in Fig. 1, antenna panel 100 typically includes two CFNs in two parallel layers. The CFNs are optionally separated by an isolating layer and are optionally sandwiched between isolating layers. Optionally, the CFN may be realized with micro-strip lines, suspended strip lines and/or waveguides, although other physical structures for RF transmission lines may be used.

[0026] In some embodiments, antenna panel 100 includes at least 16, 20 or even at least 50 (e.g., 64) cells. Optionally, antenna panel 100 includes at least 100, 250 or even at least 500 cells. Possibly, antenna panel 100 includes over 1000 or even over 1500 cells. Suggested practical numbers of cells for some exemplary embodiments are 128, 144, 256 and 576 and/or other numbers that are preferably divisible by 16 and/or are squares of other numbers.

[0027] Each cell optionally may have an area of less than 2 square centimeters, less than 1.4 centimeters or even not more than 1 square centimeter. Optionally, antenna 100 can be used for efficient data transmission and/or reception over a large frequency band, for example at least 1 GHz or even at least 4 or 5 GHz, when designed for Ku-band operation. In some embodiments, the antenna may have a bandwidth of less than 8 GHz, less than 6 GHz and in some cases less than 4 GHz. Antenna 100 optionally can be used for transmission with a relative bandwidth greater than 10%, 20% or even greater than 30%. In an exemplary embodiment, antenna 100 is designed to operate with a central frequency within the Ku band, i.e., the band between 10-18 GHz, and an absolute bandwidth of at least 3 GHz or even at least 3.5 GHz, for example about 3.8 GHz. Optionally, the antenna may be designed for the 10.7 - 14.5 GHz band.

[0028] In some embodiments, each cell 102 has a gain of between about 5-8 dB, for example 6 dB, although cells with other gains may be used. Optionally, antenna panel 100 may include a sufficient number of cells to achieve a total gain of at least 20 dB, 25 dB or even at least 30 dB.

[0029] In RF signal transmission, a data-carrying electrical RF signal to be transmitted may be fed to central feed line 104, from which the signal may be distributed to all of cells 102 through the CFN. In some embodiments, the electrical signal may be distributed evenly (e.g., equal in magnitude and in relative phase) to each of cells 102. Each of cells 102 generates a propagating RF electromagnetic wave from the electrical signals, such that the RF waves emanating from all of cells 102 combine into an RF electromagnetic beam propagation pattern having an equal-phase wave front, and having sufficient strength for communication with a remote receiver, such as on a satellite. As will be understood, a reciprocal procedure in the opposite direction occurs when antenna panel 100 receives RF waves from a remote transmitter.

[0030] Fig. 2 is an exploded perspective view of one of cells 102, in accordance with an exemplary embodiment. Cell 102 includes an upper electrical probe 151 and a lower electrical probe 121. Probes 151 and 121 convert RF electrical signals into propagating RF electromagnetic waves (e.g., microwaves) for transmission and convert received RF microwaves into RF electrical signals in reception. Upper electrical probe 151 is located within a metal frame 150, which isolates upper probe 151 from its surroundings, e.g., other cells 102. Similarly, lower probe 121 is optionally located within a metal frame 120, for inter-cell isolation.

[0031] In some embodiments, cell 102 is surrounded by metal isolation over most of its height or even its entire height, in order to achieve good isolation from neighboring cells. As shown in Fig. 2, the isolation optionally includes, in addition to frames 150 and 120, a central enclosure 140 between probes 151 and 121, a lower enclosure 128 below lower probe 121 and an upper enclosure 144 above upper probe 151. Optionally, enclosures 128, 140 and/or 144 are formed of continuous metal walls. Alternatively or additionally, one or more of the enclosures may have a metal mesh structure. Other parts of exemplary cell 102 are described below.

Probes

[0032] Probes 121 and 151 are optionally quarter wavelength monopole radiating elements. Alternatively, probes 121 and 151 may be of any other type of radiating element known in the art as useful for panel antennas, such as any of the probes described in above mentioned U.S. patent 5,872,545 to Rammos. In some embodiments, probes 151 and 121 are formed on respective dielectric substrates 154 and 124 located within the respective frames 150 and 120 of the probes (e.g., thin PCB substrate for each cell or a larger substrate with formed arrays of conductive traces 151, 121, 150, 120 for each cell). In an exemplary embodiment, probes 151 and 121 are made of copper, although other conductive metals, such as silver or gold, may be used.

[0033] Probes 121 and 151 optionally have a rectangular shape, for ease of design and/or electrical operation. In some embodiments, probes 121 and 151 have a length which is at least 50%, at least 65% or even at least twice their widths. Optionally, probes 121 and 151 are both of the same size, so as to operate with antenna gains of the same magnitudes and/or frequency response. Alternatively, probes 121 and 151 may have different sizes, for example corresponding to respective different wavelengths with which they are to operate. In an exemplary embodiment, probes 121 and 151 are about 2.5mm long and about 1.5 mm wide.

[0034] Probes 121 and 151 are preferably orthogonal to each other, creating a 90° rotation in polarization between the propagating RF electromagnetic waves generated (or detected) by the probes. It will be understood that the probes are connected to a respective distal feed point of a CFN. The probe and/or its feed line pass through a small gap in the surrounding metal cell frame and are thus not shorted out to the grounded frame. In an exemplary embodiment, upper frame 150 has a square shape, with upper probe 151 extending perpendicular from the middle of one of its sides. Lower probe 121 is optionally parallel to the side of frame 150 from which probe 151 extends, although below the frame. Optionally, upper frame 150 is symmetrical around the long axis of probe 151 and around the long axis of probe 121.

Frames

[0035] Fig. 3 is a schematic illustration of probe 121, within its respective frame 120, in accordance with an exemplary embodiment. Frame 120 is optionally formed on an outer periphery of substrate 124, possibly on both faces of the substrate. In some embodiments, the portions of frame 120 on the opposite faces of substrate 124 are connected by metal which covers the thickness (the outer edge) of the substrate. Alternatively or additionally, one or more via holes 122 passing through substrate 124 electrically connect portions of frame 120 on opposite faces of substrate 124. Optionally, frame 120 comprises copper, although any other suitable conductive metal (e.g., silver, gold) may be used. In some embodiments, frame 120 comprises copper coated by another metal, such as silver or gold.

[0036] In some embodiments, substrate 124 comprises a microwave insulating material having a constant predetermined permittivity, for example a permittivity between about 2-2.6, for example 2.2 or 2.3. In an exemplary embodiment, R/T Duroid 5880 available from the Rogers Corporation from Connecticut is used as the insulating substrate material.

[0037] Frame 150 (Fig. 2) optionally has a similar structure to that of frame 120, including a substrate 154 similar to substrate 124, and via holes 152 similar to via holes 122 in frame 120. In contrast, in some embodiments, upper frame 150 has a different size and/or shape, than lower frame 120.

Dielectric Fillers

[0038] In the invention, some or all of the internal volumes of cell 102, e.g., as defined by enclosures 140 and 144, are filled with respective dielectric fillers. In an exemplary embodiment, lower enclosure 128 is filled by a lower filler 132 (Fig. 2), having a dielectric permittivity of ε_r1, upper enclosure 144 is filled by an upper filler cover 138 having a dielectric permittivity of ε_r3 and central enclosure 140 is filled by a central filler 130, having a dielectric permittivity ε_r2.

[0039] Optionally, dielectric fillers 132, 138 and 130 have the same relative dielectric permittivity values, i.e., ε_r1 = ε_r2 - ε_r3. Alternatively, different ones of the fillers may have different permittivity values, to better match impedance for the specific wavelength(s) for which probes 121 and 151 are designed. In an exemplary embodiment, ε_r1 = ε_r2 = 3 and ε_r3 is between 3 and 4.

Propagation Path From Lower Probe

[0040] Frame 120 is optionally sufficiently large so as not to interfere with generation and/or transmission of propagating RF microwave signals from lower probe 121. In an exemplary embodiment, for Ku band transmission, frame 120 has a length B2 (Fig. 3) greater than 8 millimeters or even greater than 9 millimeters (e.g., 10 millimeters). Optionally, length B2 is not substantially larger than required (e.g., using conventional rectangular waveguide design criteria) to allow the waves to propagate upwards, so as to minimize the size of each cell 102 and hence maximize the number of cells included in a given area. In some embodiments, length B2 is not more than 20%, or even not more than 10%, greater than the minimal length required to allow wave propagation. In an exemplary embodiment, for Ku band transmission, frame 120 has a length B2 smaller than 12 millimeters, smaller than 11 millimeters, or even smaller than 10 millimeters. Probe 121 is optionally located in the middle of the length B2 of the frame.

[0041] Frame 120 optionally has a width W1 (Fig. 3) which is sufficiently large not to interfere with generation and/or transmission of RF microwave signals propagating to/from lower probe 121. In an exemplary embodiment, for Ku band transmission, frame 120 has a width of at least 3, 4 or even 5 millimeters. Thus, in some embodiments, probes 121 and/or 151 have a length of at least 40%, 50% or even 70% of the length of their respective frames 120 and 150.

[0042] Fig. 4 is a cross-sectional illustration of cell 102, along line A-A' of Fig. 2, in accordance with an exemplary embodiment. Optionally, the outer walls of enclosures 140 and 144 (Fig. 2) and frame 150, which are located within cell 102 above frame 120 in the direction of arrow 190 (Fig. 2), are not located above the area defined by frame 120, in order not to interfere with the propagation of waves to/from lower probe 121. In some embodiments, above lower probe 121, cell 102 has a length B1 (Fig. 4) substantially equal to length B2 (Fig. 3), in order to minimize the size of cell 102. Alternatively, length B1 is larger than length B2, for example by at least 5% or even 10%.

[0043] The volume defined by lower enclosure 128 together with the thickness of substrate 124 optionally has a height H1 (Fig. 4), which is selected such that a bottom surface 113 of enclosure 128 mirrors back microwave signals generated by lower probe 121 that propagate downward. Thus, instead of half the energy of the generated waves propagating downwards, while only half the generated microwaves propagate upward in the transmission direction of the antenna, the reflection by bottom surface 113 causes substantially all the energy of the generated microwaves to propagate in the transmission direction (designated by arrow 190 in Fig. 2), such that bottom surface 113 serves as a reflector structure. In some embodiments, the height H1 between bottom surface 113 and probe 121 is selected as a quarter of the wavelength (λ/4) of a representative frequency (e.g., a central frequency of the intended bandwidth of the antenna) of the waves generated (or received) by probe 121, such that the distance propagated by the downward traveling signals until they return to probe 121 is λ/2. The downward propagating microwave signals from probe 121 also undergo a phase shift of 180° degrees (equivalent to a travel of λ/2) when they are reflected from a bottom surface 113 of enclosure 128, such that the returning signals undergo a total phase shift of 360° degrees (equivalent to a travel of a full λ), which is equivalent to no phase shift at all.

[0044] Enclosure 128 optionally has the same length as the length B2 of frame 120, so that the waves throughout the area of frame 120 are allowed to propagate downward through height H1.

Propagation Path From Upper Probe

[0045] The internal volume of cell 102 defined by central enclosure 140 (Fig. 2) is optionally designed in a manner which allows downward propagation of microwave signals from upper probe 151 only to a limited extent, such that the downward propagating waves are reflected upward in a manner which constructively combines with waves originally propagating upwards from probe 151. As earlier mentioned, the design is also such that it allows passage therethrough of microwaves from lower probe 121 upwards.

[0046] Fig. 5 is a cross-sectional view of the height of cell 102 beneath upper probe 151, along line B-B' of Fig. 2, in accordance with an exemplary embodiment. Immediately beneath upper probe 151 and frame 150, an upper portion 142 of enclosure 140 has a width A1, which allows unobstructed generation and propagation of waves from upper probe 151, in the intended frequency band of antenna panel 100 (Fig. 1). In an exemplary embodiment, width A1 is greater than 8 millimeters or even greater than 9 millimeters. Optionally, A1 is about 10 millimeters. In some embodiments, width A1 is substantially equal to length B1.

[0047] A mid-portion 149 of enclosure 140 optionally has a smaller width A2, which imposes a waveguide cutoff frequency that prevents downward propagation of waves generated by upper probe 151 into mid-portion 149 of enclosure 140. Thus, mid-portion 149 serves as an evanescent-mode waveguide for signals generated by upper probe 151. In an exemplary embodiment, width A2 is less than 8 millimeters or even less than 7 millimeters, optionally depending on the specific wavelengths for which the antenna panel is designed. For example, a width which blocks frequencies below 14.5 GHz may be used in a Ku band antenna. In some embodiments, upper portion 142 has a height H3, which is selected as a quarter of the wavelength (λ/4) of a representative frequency of the waves generated (or received) by probe 151, as discussed above regarding height H1 with respect to lower probe 121.

[0048] Thus, in some embodiments, enclosure 140 between upper probe 151 and lower substrate 124 has at least two different widths (A1 and A2). Width A1 of the upper portion is optionally used in order not to interfere with the operation of upper probe 151, while width A2 of the lower mid-portion prevents down propagation of waves from probe 151.

[0049] Optionally, enclosure 128 has a still lower width A3, which is even smaller than width A2 of mid-portion 149, in order to provide gradual increase in the width of cell 102 (i.e., a better impedance matching) and thus reduce signal reflections downward of upward traveling waves from lower probe 121. In an exemplary embodiment, width A3 of enclosure 128 is about 5 millimeters.

[0050] In other embodiments, width A2 is larger than required to impose a cutoff frequency, but width A3 of enclosure 128 is sufficiently small to prevent downward propagation of waves from upper probe 151. Optionally, in these embodiments, the height H2 of mid-portion 149 is equal to a quarter of the wavelength of a mid-band frequency of the microwave signals for which antenna 100 is to operate, so that signals propagating downwards from probe 151 are reflected upwards such that they have the same phase as generated signals initially propagating upwards from probe 151.

[0051] As shown, the width W1 of frame 120 is equal to width A2 of mid-portion 149. In other embodiments, the width W1 of frame 120 is equal to width A3 of enclosure 128 or is equal to an intermediate width between A2 and A3.

Central Enclosure

[0052] In addition to having a changing width, at least in the direction orthogonal to upper probe 151, the internal volume of central enclosure 140 and/or of filler 130 optionally has a cross-sectional shape which changes along the height of cell 102 (indicated by arrow 190), between upper probe 151 and lower probe 121 (Fig. 2). In some embodiments, the internal volume of central enclosure 140 and/or of filler 130 has at least two different cross-sectional shapes along the height of the cell. Optionally, near lower probe 121, the internal volume of central enclosure 140 and/or of filler 130 (Fig. 2) has a rectangular cross-sectional shape, for example similar to the shape of lower frame 120. In some embodiments, near lower probe 121, the internal volume of central enclosure 140 and/or of filler 130 is symmetrical around an axis passing through the length of lower probe 121. Optionally, the cross sectional shape near lower probe 121 is also symmetric about an axis passing through probe 151.

[0053] Near upper probe 151 the internal volume of central enclosure 140 and/or of filler 130 optionally has a capital "T" shape, which is symmetric about an axis passing through upper probe 151 but is not symmetric about an axis passing through lower probe 121. Alternatively to the "T" shape, upper portion 142 may have a rectangular, possibly square, cross section, defined by width A1 and length B1. This alternative is optionally used when an antenna panel with a tilted beam is desired, as a square shape causes a squint (i.e., tilt angle in beam angle) in the waves generated by upper probe 151.

[0054] In some embodiments, frame 150 has the same size and shape as upper portion 142 of central enclosure 140. Alternatively, for simplicity, frame 150 may have a square shape, regardless of the shape of upper portion 142. In some embodiments, frame 150 is thin (along height 190 in Fig. 2) relative to enclosure 140 and therefore the shape of frame 150 is less important than the shape of enclosure 140. Optionally, enclosure 140, frame 150 and/or other enclosures and frames of cell 102 have walls which intersect at 90° angles. Alternatively to 90° angles, rounded shapes may be used, for example with a 0.5 millimeter radius in at least some of its corners. The use of rounded corners allows in some cases simpler production.

Upper Enclosure

[0055] In some embodiments, upper enclosure 144 (Fig. 2) has a square shape, which allows passage of signals from both of probes 121 and 151, and allows relatively more simple production. Alternatively, upper enclosure 144 has a shape similar to the cross-section of upper portion 142 of enclosure 140, minimizing the area of cell 102.

[0056] Optionally, upper enclosure 144 includes a small metal ridge 160 (Fig. 2), forming a single-ridged waveguide, which improves the cell gain for lower frequencies of the frequency range. Ridge 160 optionally reduces the cutoff frequency of upper enclosure 144 and hence increases the bandwidth of cell 102.

[0057] Metal ridge 160 is optionally small enough not to cover a substantial portion of upper probe 151. Optionally, metal ridge 160 does not cover more than 20% or even more than 10% of upper probe 151. In an exemplary embodiment, metal ridge 160 does not cover any of probe 151. In some embodiments, metal ridge 160 protrudes from upper enclosure 144 not more than 1.5 millimeters, not more than 1 millimeter or even not more than 0.5 millimeters. Optionally, ridge 160 protrudes from upper enclosure 144 by at least 0.2 or even at least 0.4 millimeters. Metal ridge 160 optionally has a width of more than 1 millimeter, more than 1.5 millimeters or even more than 1.8 millimeters.

[0058] In some embodiments, the dielectric value ε_r3 of filler cover 138 (Fig. 2) is selected based on the requirements of the higher frequencies of the bandwidth range for which antenna panel 100 is designed, while metal ridge 160 corrects for the lower frequencies of the range.

Overlay Covers

[0059] In some embodiments, above upper dielectric filler cover 138, cell 102 includes one or more dielectric overlay covers 134 and 136 (Fig. 2), which serve to improve impedance matching between cell 102 and surrounding space (e.g., the atmosphere). The improved impedance matching optionally reduces signal reflections between cell 102 and the atmosphere. The dielectric values of covers 134 and 136 are optionally selected for improved impedance matching, using methods known in the art.

[0060] Fig. 6 is a schematic sectional view of an antenna panel 600 beneath a radome 602, in accordance with an exemplary embodiment Antenna panel 600 comprises a plurality of cells 102, each of which includes a main body 610 (e.g., including enclosures 128, 140 and 144) and overlay covers 134 (marked 134A, 134B and 134C in Fig. 6), 136 and 138. Alternatively, one or more cells 102 include fewer overlay covers or more overlay covers, for example including an additional overlay cover 192.

[0061] Radome 602 optionally seals antenna panel 600 from external humidity, dust and/or other interfering particles of the environment.

[0062] In some embodiments, the covers 134 of different cells have different dielectric properties. Optionally, the covers 134 have dielectric properties at least partially selected according to the average dielectric properties of the radome above each cell. In an exemplary embodiment, covers 134A of cells located under a front portion 610 of radome 602 have first dielectric value, covers 134B of cells beneath a central portion 612 of radome 602 have a second dielectric value, and covers 134C of cells 102 beneath a rear portion 614 of radome 602 have a third dielectric value. This embodiment is optionally used, when antenna panel 600 is not rotated, or is rotated together with radome 602.

[0063] In some embodiments, antenna panel 600 is rotated relative to radome 602. The dielectric values of covers 134 are optionally selected, among other factors, according to the average dielectric value of the radome above the cell.

[0064] The variations in the dielectric properties may be achieved in many methods, one or more of which may be used as appropriate. In some embodiments, dielectric covers 134 are parallel to the probes of the cells 102 and differ in their dielectric value, for example the material from which they are formed. Alternatively or additionally, the dielectric covers 134 of different cells 102 differ in their dimensions, for example in their thickness. Further alternatively, some or all of the dielectric covers 134, of some or all of the cells 102, are tilted at an angle relative to the probes of the cells. In some embodiments of the invention, at least some of the dielectric covers 134 of at least some of the cells have a non-uniform thickness and/or covers of different cells have different thicknesses.

[0065] While the above description relates to variations in the dielectric values of covers 134, in some embodiments there are also, or alternatively, variations in the dielectric values of covers 136 and/or 138.

[0066] It is noted that the use of covers 134 having different dielectric properties is not limited to use in matching radome properties but may be used for other purposes, such as adding a tilt to the beam direction of the antenna panel, such that the beam direction is not perpendicular to the surface of the antenna panel.

Conclusion

[0067] It is noted that although the above discussion relates in many places to transmission of signals by probes 151 and 121, the same principles generally govern the reception of signals by the probes and one or both of the probes may be used for signal reception.

[0068] Antennas in accordance with the above described embodiments may be used for substantially any type of communications required, including direct broadcast television satellite (DBS) communications and/or Internet access through satellite. The antennas may be used with fixed orbital position (geostationary) satellites, low orbit satellites and/or any other satellites.

[0069] An antenna panel structure as described herein may be used as each sub-panel in a splitpanel array as described in U.S. patent US 7629935 B2

[0070] The above described antenna panels are used for microwave signals in dual-polarizations, for example using both horizontal and vertical polarizations, and/or one or both of RHCP and LHCP (Right-Hand-Circular-Polarization & Left-Hand-Circular-Polarization), or propagating RF electromagnetic waves having any other desired polarization. In some examples, the beam direction of the antenna panel is perpendicular to the surface of the antenna. Alternatively, the beam direction may be squinted and/or tilted relative to a perpendicular to the surface of the antenna panel.

[0071] It will be envisioned that the above described apparatus may be varied in many ways, including, changing the materials used and the exact structures used. The number of substrate layers may be adjusted, for example placing the probes and frames on different substrates. Substantially any suitable production method for the antenna may be used. It should also be appreciated that the above described description of methods and apparatus are to be interpreted as including apparatus for carrying out the methods and methods of using the apparatus.

Claims

1. An RF antenna structure, comprising a plurality of arrayed radiation cells (102), each cell (102) comprising:

a) an upper probe (151);

b) a lower probe (121) spaced away from said upper probe (151), and oriented at 90 degrees so as to excite an orthogonally polarized wave as compared to a wave excited by the upper probe (151);

c) a conductive enclosure (140) situated between the upper and lower antenna probes (121,151), wherein the enclosure (140) comprises an upper portion (142) and a lower portion (149) having differing cross-sections, and wherein said cross-sections are orthogonal to the propagation direction of the RF waves through said conductive enclosure (140);

d) said lower portion (149) defining a waveguide of a first rectangular cross-section, and wherein said lower portion's cross-section is configured to substantially pass RF waves transmitted/received by the lower probe (121), and to substantially prevent passage of RF waves transmitted/received by the upper probe (151); and

e) said upper portion (142) defining a waveguide of a second cross-section, and configured to substantially pass RF waves transmitted/received by the lower probe (121) as well as the upper probe (151);
characterized by:

said conductive enclosure (140) contains a dielectric filler (130),

the cross-section of said upper portion (142) comprises a superposition of said lower portion's cross-section being said first rectangle with a second rectangle, a longest dimension of said second rectangle being oriented at 90 degrees with respect to a longest dimension of said lower portion's cross-section, thereby defining a T-shaped cross-section; and

said enclosures (140) being adapted for operation over a bandwidth of 10.7 to 14.5 GHz.

2. An RF antenna structure as in claim 1, comprising at least 64 said radiation cells (102).

3. An RF antenna structure as in any of the preceding claims, wherein the conductive enclosure (140) comprises a substantially continuous metallic enclosure adapted to isolate waves generated within cell (102) from neighboring cells of the antenna structure.

4. An RF antenna structure as in any of the preceding claims, wherein the antenna is configured as a planar array antenna structure.

5. An RF antenna structure as in any of the preceding claims, wherein the at least one radiation cell (102) is adapted for transmission of waves of a predetermined frequency band and wherein the upper portion (142) allows propagation of waves generated by the upper probe (151) in the predetermined frequency band while the lower portion (149) does not substantially allow propagation of waves generated by the upper probe (151) in the predetermined frequency band.

6. An RF antenna structure as in any of the preceding claims, wherein the height of the upper portion (142) of the enclosure (140) is substantially equal to a quarter wavelength of a frequency that can pass through the upper portion (142) but is blocked from passing below the upper portion (142).

7. An RF antenna structure as any of the receding claims, comprising at least one dielectric cover (134) above the cell conductive enclosure (140).

8. An RF antenna structure as in claim 7, wherein the at least one dielectric cover (134) is not perpendicular to a beam direction of the cell (102).

9. An RF antenna structure as in claim 7 or claim 8, wherein the at least one dielectric cover (134) has a non-uniform thickness.

10. An RF antenna structure as in any of the preceding claims, wherein the enclosure (140) comprises a metal ridge (160), smaller than the upper probe (151), serving as a ridged waveguide structure.

11. An RF antenna structure as in claim 1, wherein the conductive enclosure (140) includes a waveguide section that passes RF waves with the polarization of the lower probe (121) but is cut-off for RF waves with the polarization of the upper probe (151).

12. An RF antenna structure as in claim 11, wherein the conductive enclosure (140) is spaced at a distance from the upper probe (151) such that RF waves reflected from the conductive enclosure (140) reinforce RF waves generated or received at the upper probe (151).

13. An RF antenna structure as in any of the preceding claims, wherein said upper portion's cross-section is symmetric about an axis passing through said upper probe (151), but is not symmetric about an axis passing through said lower probe (121).

14. An RF antenna structure as in any of the preceding claims, having a relative bandwidth greater than 30%.

15. An RF antenna structure as in any of the preceding claims, wherein a width of said lower portion (149) imposes a cutoff frequency that prevents propagation of RF waves transmitted/received from upper probe (151) towards lower probe (121).

16. An RF antenna structure as in any of the preceding claims, wherein said antenna structure is configured for simultaneous transmission and reception.

Ansprüche

1. Eine RF-Antennenstruktur, umfassend eine Mehrzahl angeordneter Strahlungselemente (102), wobei jedes Strahlungselement (102) umfasst:

a) eine obere Sonde (151);

b) eine untere Sonde (121) beabstandet bezüglich der genannten oberen Sonde (151) und um 90 Grad ausgerichtet, um eine orthogonal polarisierte Welle anzuregen, im Vergleich zu einer Welle angeregt durch die obere Sonde (151);

c) ein leitendes Gehäuse (140) angeordnet zwischen den oberen und unteren Antennensonden (121, 151), wobei das Gehäuse (140) ein oberes Teil (142) und ein unteres Teil (149) mit unterschiedlichen Querschnitten umfasst, und wobei die genannten Querschnitte orthogonal zur Ausbreitungsrichtung der RF-Wellen durch das genannte leitende Gehäuse (140) sind;

d) das genannte untere Teil (149) definiert einen Wellenleiter mit einem ersten rechteckigen Querschnitt, und wobei der Querschnitt des genannte untere Teils ausgestaltet ist um im Wesentlichen die von der Sonde (121) ausgesendeten/ empfangenen RF-Wellen durchzulassen, und um im Wesentlichen den Durchtritt der von der oberen Sonde (151) ausgesendeten/empfangenen RF-Wellen zu verhindern; und

e) der genannte obere Teil (142) definiert einen Wellenleiter mit einem zweiten Querschnitt, und ist ausgestaltet um im Wesentlichen RF-Wellen, ausgesendet/empfangen durch die untere Sonde (121) als auch durch die obere Sonde (151), durchzulassen;
dadurch gekennzeichnet,:

dass das genannte leitende Gehäuse (140) einen dielektrischen Füllstoff (130) enthält,

dass der Querschnitt des genannten oberen Teils (142) eine Überlagerung des genannten Querschnittes des unteren Teils umfasst,

welcher das genannte erste Rechteck mit einem zweiten Rechteck ist,

eine längste Dimension des genannten zweiten Rechtecks ist um 90 Grad orientiert bezüglich zu einer längsten Dimension des Querschnittes des genannten unteren Teils, sodass ein T-förmiger Querschnitt definiert ist; und

dass das genannte Gehäuse (140) ausgestaltet ist zum Betrieb über eine Bandbreite zwischen 10.7 und 14.5 GHz.

2. RF-Antennenstruktur gemäss Anspruch 1, umfassend zumindest 64 der genannten Strahlungselemente (102).

3. RF-Antennenstruktur gemäss einem der vorhergehenden Ansprüche, wobei das leitende Gehäuse (140) ein im Wesentlichen durchgängiges metallisches Gehäuse umfasst, ausgestaltet zum Isolieren von Wellen innerhalb des Strahlungselementes (102), welche von benachbarten Strahlungselementen der Antennenstruktur erzeugt sind.

4. RF-Antennenstruktur gemäss einem der vorhergehenden Ansprüche, wobei die Antenne als Planargruppenantennenstruktur ausgestaltet ist.

5. RF-Antennenstruktur gemäss einem der vorhergehenden Ansprüche, wobei das zumindest eine Strahlungselement (102) ausgestaltet ist zum Senden von Wellen eines vorherbestimmten Frequenzbandes, und wobei der obere Teil (142) eine Ausbreitung von durch die obere Sonde (151) in einem vorherbestimmten Frequenzband erzeugten Wellen erlaubt, wogegen der untere Teil (149) im Wesentlichen eine Ausbreitung von Wellen, erzeugt durch die obere Sonde (151) im vorbestimmten Frequenzband, nicht erlaubt.

6. RF-Antennenstruktur gemäss einem der vorhergehenden Ansprüche, wobei die Höhe des oberen Teils (142) des Gehäuses (140) im Wesentlichen gleich einer Viertelwellenlänge einer Frequenz ist, die den oberen Teil (142) durchlaufen kann, die aber geblockt ist vom Durchlaufen unterhalb des oberen Teils (142).

7. RF-Antennenstruktur gemäss einem der vorhergehenden Ansprüche, umfassend zumindest eine dielektrische Abdeckung (134) oberhalb des leitenden Gehäuses (140) des Elementes.

8. RF-Antennenstruktur gemäss Anspruch 7, wobei zumindest eine dielektrische Abdeckung (134) nicht senkrecht zu einer Strahlrichtung des Elementes (102) verläuft.

9. RF-Antennenstruktur gemäss Anspruch 7 oder 8, wobei die zumindest eine dielektrische Abdeckung (134) eine ungleichmässige Dicke aufweist.

10. RF-Antennenstruktur gemäss einem der vorhergehenden Ansprüche, wobei das Gehäuse (140) einen Metallsteg (160) umfasst, welcher kleiner als die obere Sonde (151) ist, und welcher als eine Stegwellenleiterstruktur dient.

11. RF-Antennenstruktur gemäss Anspruch 1, wobei das leitende Gehäuse (140) einen Wellenleiterabschnitt umfasst, der RF-Wellen mit der Polarisation der unteren Sonde (121) durchlässt, jedoch RF-Wellen mit der Polarisation der oberen Sonde (151) abschneidet.

12. RF-Antennenstruktur gemäss Anspruch 11, wobei das leitende Gehäuse (140) derart beabstandet zur oberen Sonde (151) ist, dass vom leitenden Gehäuse (140) reflektierte RF-Wellen die von der oberen Sonde (151) erzeugten und empfangenen RF-Wellen verstärken.

13. RF-Antennenstruktur gemäss einem der vorhergehenden Ansprüche, wobei der Querschnitt des genannten oberen Teils symmetrisch bezüglich einer durch die obere Sonde (151) verlaufenden Achse ist, jedoch nicht symmetrisch bezüglich einer durch die untere Sonde (121) verlaufenden Achse ist.

14. RF-Antennenstruktur gemäss einem der vorhergehenden Ansprüche, aufweisend eine relative Bandbreite von grösser als 30%.

15. RF-Antennenstruktur gemäss einem der vorhergehenden Ansprüche, wobei eine Breite des genannten unteren Teils (149) eine Trennfrequenz aufzwingt, welche ein Ausbreiten von RF-Wellen, gesendet / empfangen von der oberen Probe (151) gegen die untere Probe (121), verhindert.

16. RF-Antennenstruktur gemäss einem der vorhergehenden Ansprüche, wobei die genannte Antennenstruktur ausgestaltet ist zum gleichzeitigen Senden und Empfangen.

Revendications

1. Structure d'antenne à radio fréquence (RF), comprenant une pluralité de cellules de rayonnement mises en réseau (102), chaque cellule (102) comprenant :

a) une sonde supérieure (151) ;

b) une sonde inférieure (121) espacée de ladite sonde supérieure (151), et orientée à 90 degrés de façon à exciter une onde polarisée orthogonalement par comparaison à une onde excitée par la sonde supérieure (151) ;

c) une enceinte conductrice (140) située entre les sondes d'antenne inférieure et supérieure (121, 151), où l'enceinte comprend une partie supérieure (142) et une partie inférieure (149) présentant des sections transversales différentes, et où lesdites sections transversales sont orthogonales à la direction de propagation des ondes RF au travers de l'enceinte conductrice (140) ;

d) ladite partie inférieure (149) définissant un guide d'onde présentant une première section transversale rectangulaire, et où la section transversale de ladite partie inférieure est configurée pour laisser passer globalement les ondes RF émises/reçues par la sonde inférieure (121), et pour empêcher globalement le passage d'ondes RF émises/reçues par la sonde supérieure (151) ; et

e) ladite partie supérieure (142) définissant un guide d'onde présentant une deuxième section transversale, et configurée pour laisser passer globalement les ondes RF émises/reçues par la sonde inférieure (121) ainsi que par la sonde supérieure (151) ;
caractérisée par :

ladite enceinte conductrice (140) contient une charge diélectrique (130),

la section transversale de ladite partie supérieure (142) comprend une superposition de la section transversale de ladite partie inférieure constituant ledit premier rectangle avec un deuxième rectangle, une dimension la plus longue dudit deuxième rectangle étant orientée à 90 degrés par rapport à une dimension la plus longue de la section transversale de ladite partie inférieure, en définissant ainsi une section transversale en forme de T ; et

ladite enceinte (140) étant conçue pour un fonctionnement sur une largeur de bande de 10,7 à 14,5 GHz.

2. Structure d'antenne RF selon la revendication 1, comprenant au moins 64 dites cellules de rayonnement (102).

3. Structure d'antenne RF selon l'une quelconque des revendications précédentes, dans laquelle l'enceinte conductrice (140) comprend une enceinte métallique globalement continue conçue pour isoler les ondes générées à l'intérieur de la cellule (102) des cellules voisines de la structure d'antenne.

4. Structure d'antenne RF selon l'une quelconque des revendications précédentes, dans laquelle l'antenne est configurée sous forme d'une structure d'antenne-réseau plane.

5. Structure d'antenne RF selon l'une quelconque des revendications précédentes, dans laquelle la au moins une cellule de rayonnement (102) est conçue en vue d'une transmission d'ondes d'une bande de fréquences prédéterminée et dans laquelle la partie supérieure (142) permet la propagation d'ondes générées par la sonde supérieure (151) dans la bande de fréquences prédéterminée alors que la partie inférieure (149) ne permet globalement pas la propagation d'ondes générées par la sonde supérieure (151) dans la bande de fréquences prédéterminée.

6. Structure d'antenne RF selon l'une quelconque des revendications précédentes, dans laquelle la hauteur de la partie supérieure (142) de l'enceinte (140) est pratiquement égale à un quart de longueur d'onde d'une fréquence qui peut traverser la partie supérieure (142) mais qui est empêchée de passer en dessous de la partie supérieure (142).

7. Structure d'antenne RF selon l'une quelconque des revendications précédentes, comprenant au moins une protection diélectrique (134) au-dessus de l'enceinte conductrice de cellule (140).

8. Structure d'antenne RF selon la revendication 7, dans laquelle la au moins une protection diélectrique (134) n'est pas perpendiculaire à une direction de faisceau de la cellule (102).

9. Structure d'antenne RF selon la revendication 7 ou la revendication 8, dans laquelle la au moins une protection diélectrique (134) présente une épaisseur non uniforme.

10. Structure d'antenne RF selon l'une quelconque des revendications précédentes, dans laquelle l'enceinte (140) comprend une nervure métallique (160), plus petite que la sonde supérieure (151), servant de structure de guide d'onde à nervure.

11. Structure d'antenne RF selon la revendication 1, dans laquelle l'enceinte conductrice (140) comprend une section de guide d'onde qui laisse passer les ondes RF présentant la polarisation de la sonde inférieure (121) mais bloque les ondes RF présentant la polarisation de la sonde supérieure (151).

12. Structure d'antenne RF selon la revendication 11, dans laquelle l'enceinte conductrice (140) est espacée à une certaine distance de la sonde supérieure (151) de sorte que les ondes RF réfléchies de l'enceinte conductrice (140) renforcent les ondes RF générées ou reçues au niveau de la sonde supérieure (151).

13. Structure d'antenne RF selon l'une quelconque des revendications précédentes, dans laquelle la section transversale de ladite partie supérieure est symétrique autour d'un axe traversant ladite sonde supérieure (151), mais n'est pas symétrique autour d'un axe traversant ladite sonde inférieure (121).

14. Structure d'antenne RF selon l'une quelconque des revendications précédentes, présentant une largeur de bande relative supérieure à 30 %.

15. Structure d'antenne RF selon l'une quelconque des revendications précédentes, dans laquelle une largeur de ladite partie inférieure (149) impose une fréquence de coupure qui empêche la propagation des ondes RF émises/reçues de la sonde supérieure (151) vers la sonde inférieure (121).

16. Structure d'antenne RF selon l'une quelconque des revendications précédentes, où ladite structure d'antenne est configurée pour une émission et une réception simultanées.

Drawing